C4A and cancer: The most promising candidates that were up‐ or downregulated in cancer versus both the benign and healthy groups and were identified as the only protein in at least one gel spot were A2M, APOA4, C4A, CFB, CFHR2, FGG, HP, HPR, PITPNA, SERPINA1, SERPINC1, TF, and GC/VDBP.